Pulse separation circuit



March 21, 1961 R. L. UPHOFF ET AL 2,976,490

PULSE SEPARATION CIRCUIT Filed Aug. 7, 1959 {38 [4O Signal l0 2 Phase Source Amplmer', inverter [2 22 ,24 22 1 Amplifier Differeniiotor 30 {i2 44 34 28 Amplifier Mix'er -Amplifier I l r E? Phase inverter 12 1 46 Phase Lute M 5O\ lnverier y Cathode Delay Amplifier Follower Line 1 76 Delay Line Amplifier I6 82 P84 80 SchmiH hose Early i gg Inverter Gate -Ampl|f|er o iza 98 i: log L104 M2 H8 ml kg? 94 A 20 KTOZ F2 5 ll |l|l mis il l l l I I I 74 ll kl II III I ll HT I/2ms 88 F|g.'l

E l Ll m 1 i 2 88 F ii ii i ll ill ii iii l/2ms-i|" s II II T III I H l H l [J Li 1 1 ll ll u ll ll ll INVENTORS J I H H H H H Russel L.Uphoff8r John F. Loycok.

PULSE SEPARATION CIRCUIT Filed Aug. 7, 1959, Ser. No. 832,228 7 Claims. (Cl. 328-110) This invention relates to circuit apparatus for separatmg relatively short voltage pulses from long voltage'pedestals on which they are superimposed. More particularly, the invention relates to apparatus for not only separating the aforesaid short pulses, but also for converting all of the separated pulses to one polarity.

The present invention has as its principal object the provision of electrical circuitry for separating intelligence signals in the form of voltage pulses from a square wave signal on which they are superimposed. The invention has application in installations where, for example, an electron-optics device scans an image of the surface of a bright object having areas of greater or lesser brightness thereon. In such an arrangement, a relatively long voltage pedestal will be produced each time the electron beam scans the image of the surface of the bright object. Superimposed upon this voltage pedesal are positive and negative short voltage pulses produced when the electron beam of the electron-optics device scans the image of brighter and darker areas, respectively. In order to utilize the intelligence regarding the bright and dark areas, it is necessary to separate the aforesaid short cur in time at the points where the input signal A changes from one voltage level to another. This wave form is shown as wave form B in Fig. 2.-' As the voltage changes in a positive direction, the sharp pulse produced by the difierentiator is also positive, and thus a sharp positive voltage pulse is produced-at the leading edge of each pedestal and each positive pulse in the original wave form. On the other hand, a sharp negative pulse is produced at the trailing edge of each positive pulse or pedestal. In the'case of negative pulses such as pulse 20, however, the situation is'reversed. That is, a negative sharp pulse'is produced at the leading edge while a sharp positive pulse is produced at the trailing edge. I

The pulse separation circuit 26 includes a pair of diodes 28 and 30, each having one of its electrodes connected I to ground. It will be noted that the polarities of these diodes are reversed. Thus, diode 28 will pass positive pulses in wave form B to lead 32; whereas, diode 30 will pass negative pulses in the wave form to lead 34. The signals appearing on leads 32 and 34 are, therefore, the

positive and negative halves, respectively, of wave form B; The sharp voltage pulses on lead 34 are applied to an amplifier 36. Since the original signal fed to this ampli fier had only negative pulses therein, the pulses appearing at its output will be inverted in phase and of positive polarity. In a similar manner, positive pulses passing voltage pulses from the pedestals on which they are superdetailed description taken in connection with the accompanying drawings which form a part of this specification and in which:

Figure 1 is a schematic circuit diagram of a preferred embodiment of the invention; and

- Figure 2 illustrates wave forms appearing at various points in the circuit of Figure 1. v j Referring now to Figs. 1 and 2, output signals from a signal source, generally indicated at 10, are applied to each of three signal channels 12, 14 and 16. The output of signal source 10 will appear as wave form A in Fig. 2 and comprises a series of voltage pedestals or square waves having short positive and negative pulses 18 and 20 superimposed thereon. Although only two pulses are shown in the wave form A, it should be understood that the number of short pulses may vary, depending upon circumstances. In addition, the pulses may either be of alternate polarities as shown, or all of one polarity.

' In channel 12 wave form A is fed through an amplifier 22 and diiferentiator 24 to a pulse separation circuit 26. As is well known to those skilled in the art, diffe'rentiator 24 is a circuit in which the voltage amplitude at the output is proportional at any instant to the rate of'change of voltage amplitude in the input. The voltage wave form appearing'at the output of the differentiator will,-;.

through diode 28. and appearing on lead 32 are fed to an amplifier 38 where they are inverted in phase. The output of amplifier 38 will, therefore, be a series of negative, sharp voltage pulses. Consequently, these pulses are passed through a phase inverter 40 which again con verts them to positive pulses. The positive pulses at the outputsof circuits 36 and 46 are then fed to a mixer 42.

The output' of mixer 42 will appear as wave form C in Fig. 2 where a sharp spiked pulse appears at the leading and trailing edge of each pulse or pedestal in wave form A. In this case, however, all of the spiked pulses are of-the same polarity (namely, negativelbecause of the combined action of circuits 26, 36, 33, 40 and 4 2. The output of mixer 42, appearing as wave form C, is then fed through amplifier 44 and phase inverter 46 in channel 12 to a late gate circuit 48 in channel 14. 5

Thesignal from source 10 in channel 14 is first'ffed through an amplifier 50 and cathode'foll'ower 52 to d delay line 54 which will delay the original Wave forni A by one-half microsecond. Thus, the output of the delay line 54 will appear as wave form D in Fig. 2. .The' output of delay 1ine 54is applied through capacitorS S and resistor 58 to thegrid of one of 'two triode tubes 6!) and- 62in a Schmitt'triggercircuit 56. It will be; noted that the cathodes of triodes 60 and 62 in Schnu'tt trigger r circuit 56 are connected to ground through a common resistor 64; Furthermore, the anode of triode is connected'to the grid of triode 62 through the parallel come binatio'n'of capacitor 66 and resistor 68. f

Under normal conditions, triode 62 will conduct while triode 60 is cut oif. However, whenever the voltagelevel of wave form D at the output of delay line 54 rises above level 70 indicated inFig. 2, conduction will be initiated in;

triode 60. This action will cut off triode 62 because-of the'fallfin the plate voltage of triode 60 whichis coupl'ed to-the grid of triode :62through elements 66 and 68 7 plate? of t'riode'62. is, therefore, a series of po'sitive'sqiiare Triode 60'will continue to conduct until thevOltag'e lever of the pulse wave form D falls belowthat indicated by the numeral 70, at which time it will cutoff and'triodi 62 T will 'againconduct. The output appearing at wave pulses each of which has a pulse widthequaltothe widih of the voltage pedestals inwave form D; The oii't-f pu'tiof S :h1'nitt -trig'ger 56 thus appears as wave'fforin E i'n' Fig; :2 1; This wave :form. is .fed'through a phase inverter 1: 72totthei-1ate gatecircuit48. Itshould; be rememberedi amass noted that since wave formssD and :E are delayed by one-half microsecond with respect to the original wave form A, the,spiked1pulse 74 inwave forin Cdue ito-the leadingledge of eachpedestal in wave form A does not coincide intinie with the; pulsesin wave formE. on-

sequently, Qthe -pulses7 4 will be eliminated .inlate gate 48 to produce waveform F in Fig-2 wherein fall-but pulses 7 4remain.

v The output of late gate circuit 48 is then applied through a second one-halfmicroseconddelay line}7 6 and amplifier 78. to an early gate-circuit 80 in channel 16, The output of amplifier 78, therefore, will appear as wave form G which is identical to waveform F except thatit has been delayed by one-half microsecond.

Reverting againto the signal source 10, its output is also an as waveform A in Fig. 2 to channel.16 which includes a Schmitt trigger circuit 82 similar to circuit 56 already described. Thus, the output of the Schmitt trigger circuit 82 will appear as: wave form H in Fig. 2 wherein a pulse is produced for each pedestal in wave form A, these pulses having the same pulse width and phase posi tion as the original pedestals. Afterpassing through phase inverter 84, the waveform H is applied to the early gate circuit 80 which will pass signals vto amplifier 86 only upon coincidence of pulses in waveform H with thosein wave formG. It can be seen from an inspection of, Fig.2. that since wave form G. has been delayed by one-halt microsecond, the sharp voltage. pulse 88 due'to the trailing edge of each pedestal in the original wave form A does not coincide with a pulse in wave form H. Consequently, these pulses will be eliminatedat the outputof early; gate circuit 80 to produce wave form I wherein only the sharp spiked pulses due. to the leading and .trailing edges of short pulses 18 and 20 in the original wave form A remain. The one-half microsecond delay-illustrated above is, of course, not critical, it being necessary only that the delay is suflicient to eliminate pulses 18 and 20. Actually, the delay should be kept as small as possible in order to prevent the elimination of intelligence pulses which are superimposed .on .the pedestalclose to its leading and trailing .edges.;. p {The pulses in wave from I are then fed to a flipflop circuit, generally indicated at 90, which includes two triode tr bes 92 and 94. It can be seen that the cathodes of t i od,es 9 2 and 94 are both connected to ground through asingleresistor 96 as were the cathodes of triodes 60 now driven negative.

initially conducts more heavily than the other. This initialhiffereiice'in' conduction brings about a cumulative increase in the end balance as follows: It will be assumed that triode 92 initially conducts more heavily than triode 94. The increased current in triode 92 causes an increase in thevoltage drop across resistor 100; and, thus, a decrease in't he plate voltage of tube 92. Because of -'the-connection* between the plate of triode 92 and the grid of triode 94, the decrease in the plate voltageof' triode 92' is accompanied by a decrease in the 'grid voltage of triode 9 4,Thus, an increase in the platecurrent of tube 92 must beac'companied by a decrease inthe plate current of tube 94 since its grid is Moreover, the decrease of plate current through-tube 94 causes an increase'in grid voltage of triode 92 and, consequently, results in a further increase of plate current through triode 92. In this man- ,ner, a slightinitial unbalance sets up a cumulative'or regenerative switching action which reduces the plate current of tube 94 to zero and increases the plate current of tube 92- toa maximum. Though described as it occurredslowly, this switching action occurs with extreme rapidity-in a fraction of a microsecondin most flip-flop circuits.

-The -pulses in wave form I from amplifier 86 are applied tothe grids of triodes 92. and 94 through diodes 1 1-4, and 116; If triode 92 is conducting, these pulses, which are negative at the output of amplifier 86, cut ofi triode9 2. This causes a regenerative switching action which, While triode 92 cuts ofi, triode 94 conducts. Furthermore, triode 94 will continue to conduct until then'ext pulse in wave form I is received. 'l'hispulse 1 .willnow cut ofi triode 94 and will again initiate conand 62 in Schmitt trigger 56. The plate of triode 94 is connected-to a B+ voltage source through resistor 98; whereasthe plate of triode 92 is .connected to the same source of voltage through resistor 100. The grid of triode 92 is connected to ground through resistor.102 and-to the ;B-{- voltage source through resistors Hand 98, with resistor. 104 being bypassed by capacitor 106. In a similar ,manner, the grid of: triode 94 is connected to grppndthrough resistor 108 and to the B+ voltage-source through;resistors 1 1 0 and 100, with resistor 110 being bypassedbycapaeitor 112. 7 It will be noted that the plate of triode 921's connected to the grid oftriode 94 through resistor; 11!) and capacitor 112. Likewise,..the.plate of triodel94 isconnected. to the grid of triode 92through resistonllht andeapacitor 106.

Whena source of anode voltage is applied asto the flip-flop circuit, current will tend to how in theplate:

cireu its of triodes 92 and. 94.. Ifthe two halves of the: cireuitare identical, the currents willbe nearly equal' at- However, aperfect balance isalwaysdmp'ossible; andvas. will-become apparent from the following descriptiongemeanszraresprovideduto insure :thatson'e cr me tubes ductionin triode 92. This results in a pulse being prof duced'between the sharp spiked pulses in wave form I which are due to the leading and trailing edges of each short pulse 18, 20 in the original wave form A. Thus, the output of the flip-flop circuit on the anode of triode Maud resistor 118 will appear as wave form J in Fig. 2. 'This wave form, in effect, constitutes the original short pulses in wave form A which have been converted toone polarity and have been separated from the volt? age pedestals on which they were superimposed.

The present invention thus provides a means for separating the pulses 18 and 20 from the remainder of the signal in wave form A and for converting these pulses to one polarity; Although the invention has been shown in connection with a certain specific'embodiment, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.

We clairrn as our invention:

1. In combination with means for producing a train of relatively long voltage pulses having short voltage pulses superimposed thereon, circuit means for separating the short'pulses from the relatively long pulses com prising, in combination, apparatus responsive to said train of voltage pulses for producing a spiked pulse at the leading and trailing edge of each pulse in said train of pulses, means for eliminating the spiked pulses due to the leading and trailing edges of the relatively long pulses in said train of pulses, and means responsive to the-output of said last-named means for producing a pulse between the spiked pulses at the leadinga'nd trail; ing 'edgesof each short pulse in said train of pulses.

2.'ln=combination with means for producing a train of relatively long voltage pulses having short voltage pulses" superimposed thereon, circuit means for separatingtheshort pulses'from' the relatively long 'pulses comprising, in combination, a diflerentiator responsive to said-train of voltage pulses for producing a spiked pulse at the leading and trailing edge of each pulsein said train" of pulses, gating apparatus responsive to the original train leading and trailing edges of the relatively long pulses in said train of pulses, and a flip-flop circuit responsive to the output of said gating apparatus for producing a pulse between the spiked pulses at the leading and trailing edges of each short pulse in said train of pulses.

3. In combination With means for producing a train of relatively long voltage pulses having positive and negative short voltage pulses superimposed thereon, circuit means for separating the short pulses from the relatively long pulses and for converting the short pulses to one polarity comprising, in combination, apparatus responsive to said train of voltage pulses for producing a spiked positive pulse at one edge of each pulse in said train of pulses and a spiked negative pulse at the other edge of each pulse in said train of pulses, means for converting all of said spiked pulses to one polarity, apparatus for eliminating the spiked pulses due to the leading and trailing edges of each relatively long pulse in said train of pulses, and multivibrato-r means responsive to the output of said last-named apparatus for producing a pulse between the spiked pulses at the leading and trailing edges of each short pulse in said train of pulses.

4. In combination with means for producing a train of relatively long voltage pulses having positive and negative short voltage pulses superimposed thereon, circuit means for separating the short pulses from the relatively long pulses and for converting the short pulses to one polarity, comprising, in combination, apparatus responsive to said train of voltage pulses for producing a spiked positive pulse at one edge of each pulse in said train of pulses and a spiked negative pulse at the other edge of each pulse in said train of pulses, means for separating the spiked negative pulses from the spiked positive pulses, means for inverting the phase of said spiked negative pulses, a device for recombining the sep arated spiked pulses to produce a resultant signal in which all spiked pulses are of one polarity, apparatus responsive to the output of said device for eliminating the spiked pulses due to the leading and trailing edges of each relatively long pulse in said train of pulses, and apparatus responsive to the output of said last-named apparatus for producing a pulse between the spiked pulses at the leading and trailing edges of each short pulse in said train of pulses.

5. In combination with means for producing a train of relatively long voltage pulses having positive and negative short voltage pulses superimposed thereon, circuit apparatus for separating the short pulses from the relatively long pulses and for converting the short pulses to one polarity comprising, in combination, a differentiator responsive to said train of voltage pulses for producing a positive spiked pulse at one edge of each pulse in said train of pulses and a negative spiked pulse at the other edge of each pulse in the train, means for converting all of said spiked pulses to one polarity, means responsive to said train of pulses for producing first and second gating signals, means for delaying the first gating signal by a predetermined amount, first means for gating said spiked pulses with the delayed first gating signal whereby the spiked pulses due to the leading edges of the relatively long pulses in said train are eliminated, means for delaying the spiked pulses after passing through said first gating means, second means for gating the delayed spiked pulses with said second gating signal whereby the spiked pulses due to the trailing edges of the relatively long pulses in said train are eliminated, and a device responsive to the spiked pulses after pasing through the second gating means for producing a third pulsed signal in which a pulse is formed between the leading and trailing edges of each short pulse in the original train of pulses.

6. In combination with means for producing a train of relatively long voltage pulses having positive and negative short voltage pulses superimposed thereon, circuit apparatus for separating the short pulses from the relatively long pulses and for converting the short pulses to one polarity comprising, in combination, a diiierentiator responsive to said train of voltage pulses for producing a positive spiked pulse at one edge of each pulse in said train of pulses and a negative spiked pulse at the other edge of each pulse in the train, means for converting all of said spiked pulses to one polarity, means responsive to said train of pulses for producing first and second pulsed gating signals in which the pulses have the same pulse width and recurrence frequency as the relatively long voltage pulses in said train of pulses, means for delaying the first gating signal by a predetermined amount, first means for gating said spiked pulses with the delayed first gating signal whereby the spiked pulses due to the leading edges of the relatively long pulses in said train are eliminated, means for delaying the spiked pulses after passing through said firstgating means, second means for gating the delayed spiked pulses with said second gating signal whereby the spiked pulses due to the trailing edges of the relatively long pulses in said train are eliminated, and a device responsive to the spiked pulses after passing through the second gating means for producing a third pulsed signal in which a pulse is formed between the leading and trailing edges of each short pulse in the original train of pulses.

7. In combination with means for producing a train of relatively long voltage pulses having positive and negative short voltage pulses superimposed thereon, circuit means for separating the short pulses from the relatively long pulses and for converting the short pulses to one polarity comprising, in combination, first, second and third signal channels adapted for connection to said train of pulses, a difierentiator in said first channel for producing a positive spiked pulse at one edge of each pulse in said train of pulses and a spiked negative pulse at the other edge of each pulse in the train, means in said first channel for converting all of said spiked pulses to one polarity, first means in said second channel for delaying said train of pulses by a predetermined amount, further means in said second channel and responsive to the output of said first delaying means for producing a first pulsed gating signal in which the pulses have the same pulse width and recurrence frequency as the relatively long pulses in said train of pulses, a first device in said second channel for gating the output of said first channel with said first gating signal, means for delaying the output of said first gating device by a predetermined amount, means in said third channel and responsive to said train of voltage pulses for producing a sec- 0nd pulsed gating signal in which the pulses have the same pulse width and recurrence frequency as the relatively long pulses in said train of pulses, a second device in said third channel for gating the delayed output of said first gating device with said second gating signal, and a flip-flop circuit in said third channel and responsive to the output of said second gating device for producing a pulse between the spiked pulses formed by the leading and trailing edges of each short pulse in the original train of pulses.

References Cited in the file of this patent UNITED STATES PATENTS 2,648,766 Eberhard Aug. 11, 1953 2,652,450 Tourshou Sept. 15, 1953 2,699,464 Di Toro et a1. Jan. 11, 1955 2,777,059 Stites Jan. 8, 1957 2,896,077 Brandt July 21, 1959 

